1. Field of the Invention
The present invention generally relates to wireless communications networks. More particularly, the present invention relates to the switching of selectable antenna elements utilizing p-type, intrinsic, n-type (PIN) diodes thereby reducing or eliminating certain radio frequency (RF) resonance functions of the antenna element.
2. Description of the Related Art
Wireless communications systems are burdened with an ever-increasing demand for higher data throughput. These same systems are concurrently driven by the need to reduce interference that can disrupt data communications. For example, in an Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.11 network, an access point may communicate with one or more remote receiving nodes over a wireless link. The wireless link may be susceptible to interference from other access points and stations (nodes), other radio transmitting devices, changes or disturbances in the wireless link environment between the access point and the remote receiving node, and so forth. In some instances, the interference may be of such significance as to force communications across the wireless link at a lower data rate or to completely disrupt the wireless link all together.
As disclosed in, for example, U.S. patent application Ser. No. 11/010,076 and 11/041,145, Ruckus Wireless, Inc. of Sunnyvale, Calif., has utilized a series of antenna elements to produce a substantially omnidirectional radiation pattern. This pattern may be generated when two or more antenna elements are selectively coupled to an RF signal source. In some instances, this selective coupling occurs through the use of one or more PIN diodes.
Stray capacitance is an undesirable capacitance existing between two conductors. Stray capacitance may be found in the context of a PIN diode due to the semi-conducting nature of the same. Stray or “parasitic” capacitance also tends to occur between parallel traces on a printed circuit board (PCB) or between traces planes on opposite sides of a PCB. The occurrence and effects of stray capacitance are often overlooked during modeling and may lead to serious performance issues after a PCB and its constituent elements (e.g., radio equipment and antenna elements) are constructed and assembled. Stray capacitance may result in greater noise, reduced frequency response, and even system instability.
The stray capacitance of PIN diodes in an antenna array, especially in a series of PIN diodes, may hinder the operation of the antenna array and/or the components thereon. While stray capacitance may never be entirely eliminated, stray capacitance may, generally, be controlled. Stray capacitance is, therefore, a performance attribute that may drive the cost of a PIN diode. At a given operating frequency, a PIN diode with relatively low stray capacitance is typically more expensive than a PIN diode with higher stray capacitance.
In addition to expense, certain techniques for eliminating stray capacitance may require additional components to be located on or coupled to the PCB. These additional components may increase difficulties related to manufacturing and design with respect to configuring various elements in a finite space. These additional components, too, may increase the cost of manufacture.
There is a need in the art to reduce stray capacitance with respect to selective antenna elements utilizing PIN diodes. Reduction of stray capacitance should occur without significantly increasing manufacture costs. Reduction of stray capacitance should also avoid negatively affecting overall antenna design. Any reduction of stray capacitance should not interfere with the selective coupling and switching of an antenna element utilizing a PIN diode.